[PATCH v2 0/5] hvf: arm: add experimental VHE (x-vhe) toggle

[PATCH v2 0/5] hvf: arm: add experimental VHE (x-vhe) toggle

[Mohamed Mediouni]

macOS 27.0 has a pre-release VHE implementation. Add support for it in QEMU.

The first patch in the series is an independent bugfix that should be backported to QEMU 11.1 too.

v2:

Add:
hvf: arm: expose E2H0
hvf: arm: ignore accesses to CNTKCTL_EL12

This is to have working KVM under the VHE configuration.

Mohamed Mediouni (5):
  hvf: arm: advertise ID_AA64PFR0_EL1.GIC
  hvf: arm: add experimental VHE toggle
  hvf: arm: advertise EL3 support when VHE is on
  hvf: arm: expose E2H0
  hvf: arm: ignore accesses to CNTKCTL_EL12

 accel/hvf/hvf-all.c      |   2 +
 include/system/hvf_int.h |   1 +
 target/arm/hvf/hvf.c     | 114 +++++++++++++++++++++++++++++++++++++++
 target/i386/hvf/hvf.c    |   4 ++
 4 files changed, 121 insertions(+)

-- 
2.54.0 (Apple Git-156)

[PATCH v2 1/5] hvf: arm: advertise ID_AA64PFR0_EL1.GIC

[Mohamed Mediouni]

For the kernel-irqchip=on case, advertise ID_AA64PFR0_EL1.GIC.

Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
---
 target/arm/hvf/hvf.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
index da3ec521fc..f881d6cc67 100644
--- a/target/arm/hvf/hvf.c
+++ b/target/arm/hvf/hvf.c
@@ -1229,6 +1229,18 @@ static bool hvf_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
         FIELD_DP64_IDREG(&host_isar, ID_AA64PFR1, SME, 0);
     }
 
+    /*
+     * On HVF, kernel-irqchip implies GICv3.
+     * The kernel-irqchip=off,gic-version=3 legacy case also supports
+     * the host CPU interface but advertising it in ID_AA64PFR0_EL1
+     * is not implemented yet.
+     */
+
+    if (hvf_irqchip_in_kernel()) {
+        /* Advertise the GIC system register interface */
+        FIELD_DP64_IDREG(&host_isar, ID_AA64PFR0, GIC, 1);
+    }
+
     ahcf->isar = host_isar;
 
     /*
-- 
2.54.0 (Apple Git-156)

Re: [PATCH v2 1/5] hvf: arm: advertise ID_AA64PFR0_EL1.GIC

[Peter Maydell]

On Fri, 4 Sept 2026 at 05:37, Mohamed Mediouni <mohamed@unpredictable.fr> wrote:
>
> For the kernel-irqchip=on case, advertise ID_AA64PFR0_EL1.GIC.
>
> Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
> ---
>  target/arm/hvf/hvf.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
> index da3ec521fc..f881d6cc67 100644
> --- a/target/arm/hvf/hvf.c
> +++ b/target/arm/hvf/hvf.c
> @@ -1229,6 +1229,18 @@ static bool hvf_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
>          FIELD_DP64_IDREG(&host_isar, ID_AA64PFR1, SME, 0);
>      }
>
> +    /*
> +     * On HVF, kernel-irqchip implies GICv3.
> +     * The kernel-irqchip=off,gic-version=3 legacy case also supports
> +     * the host CPU interface but advertising it in ID_AA64PFR0_EL1
> +     * is not implemented yet.
> +     */
> +
> +    if (hvf_irqchip_in_kernel()) {
> +        /* Advertise the GIC system register interface */
> +        FIELD_DP64_IDREG(&host_isar, ID_AA64PFR0, GIC, 1);
> +    }

How does this interact with the existing code in
hvf_arch_init_vcpu() that does:

    pfr = GET_IDREG(&arm_cpu->isar, ID_AA64PFR0);
    pfr |= env->gicv3state ? (1 << 24) : 0;
    ret = hv_vcpu_set_sys_reg(cpu->accel->fd, HV_SYS_REG_ID_AA64PFR0_EL1, pfr);

?

env->gicv3state should be non-NULL for both HVF and TCG
GICv3, I think, so aren't we already advertising the GIC
in ID_AA64PFR0 ?

thanks
-- PMM

Re: [PATCH v2 1/5] hvf: arm: advertise ID_AA64PFR0_EL1.GIC

[Mohamed Mediouni]

> On 28. Sep 2026, at 17:54, Peter Maydell <peter.maydell@linaro.org> wrote:
> 
> On Fri, 4 Sept 2026 at 05:37, Mohamed Mediouni <mohamed@unpredictable.fr> wrote:
>> 
>> For the kernel-irqchip=on case, advertise ID_AA64PFR0_EL1.GIC.
>> 
>> Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
>> ---
>> target/arm/hvf/hvf.c | 12 ++++++++++++
>> 1 file changed, 12 insertions(+)
>> 
>> diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
>> index da3ec521fc..f881d6cc67 100644
>> --- a/target/arm/hvf/hvf.c
>> +++ b/target/arm/hvf/hvf.c
>> @@ -1229,6 +1229,18 @@ static bool hvf_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
>>         FIELD_DP64_IDREG(&host_isar, ID_AA64PFR1, SME, 0);
>>     }
>> 
>> +    /*
>> +     * On HVF, kernel-irqchip implies GICv3.
>> +     * The kernel-irqchip=off,gic-version=3 legacy case also supports
>> +     * the host CPU interface but advertising it in ID_AA64PFR0_EL1
>> +     * is not implemented yet.
>> +     */
>> +
>> +    if (hvf_irqchip_in_kernel()) {
>> +        /* Advertise the GIC system register interface */
>> +        FIELD_DP64_IDREG(&host_isar, ID_AA64PFR0, GIC, 1);
>> +    }
> 
> How does this interact with the existing code in
> hvf_arch_init_vcpu() that does:
> 
>    pfr = GET_IDREG(&arm_cpu->isar, ID_AA64PFR0);
>    pfr |= env->gicv3state ? (1 << 24) : 0;
>    ret = hv_vcpu_set_sys_reg(cpu->accel->fd, HV_SYS_REG_ID_AA64PFR0_EL1, pfr);
> 
> ?
> 
> env->gicv3state should be non-NULL for both HVF and TCG
> GICv3, I think, so aren't we already advertising the GIC
> in ID_AA64PFR0 ?

Hi,

Without this patch HVF GICv3 doesn’t show up, will look deeper at why that check
you noted is not effective…

Maybe it’s a question of ordering?
> 
> thanks
> -- PMM
> 

[PATCH v2 2/5] hvf: arm: add experimental VHE toggle

[Mohamed Mediouni]

macOS 27.0 ships with an experimental VHE enablement
private API. Expose support for it as x-vhe.

Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
---
 accel/hvf/hvf-all.c      |  2 +
 include/system/hvf_int.h |  1 +
 target/arm/hvf/hvf.c     | 89 ++++++++++++++++++++++++++++++++++++++++
 target/i386/hvf/hvf.c    |  4 ++
 4 files changed, 96 insertions(+)

diff --git a/accel/hvf/hvf-all.c b/accel/hvf/hvf-all.c
index 8bd9154a50..bbff3c6867 100644
--- a/accel/hvf/hvf-all.c
+++ b/accel/hvf/hvf-all.c
@@ -282,6 +282,8 @@ static void hvf_accel_class_init(ObjectClass *oc, const void *data)
         NULL, NULL);
     object_class_property_set_description(oc, "kernel-irqchip",
         "Configure HVF irqchip");
+
+    hvf_arch_accel_class_init(oc);
 }
 
 static const TypeInfo hvf_accel_type = {
diff --git a/include/system/hvf_int.h b/include/system/hvf_int.h
index a01691ce17..44ae2e7c4c 100644
--- a/include/system/hvf_int.h
+++ b/include/system/hvf_int.h
@@ -110,5 +110,6 @@ int hvf_update_guest_debug(CPUState *cpu);
 bool hvf_arch_cpu_realize(CPUState *cpu, Error **errp);
 uint32_t hvf_arch_get_default_ipa_bit_size(void);
 uint32_t hvf_arch_get_max_ipa_bit_size(void);
+void hvf_arch_accel_class_init(ObjectClass *oc);
 
 #endif
diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
index f881d6cc67..b61554e108 100644
--- a/target/arm/hvf/hvf.c
+++ b/target/arm/hvf/hvf.c
@@ -22,6 +22,7 @@
 #include "cpu-sysregs.h"
 
 #include <mach/mach_time.h>
+#include <dlfcn.h>
 
 #include "system/address-spaces.h"
 #include "system/memory.h"
@@ -39,6 +40,7 @@
 #include "target/arm/trace.h"
 #include "trace.h"
 #include "migration/vmstate.h"
+#include "migration/blocker.h"
 
 #include "gdbstub/enums.h"
 
@@ -1132,6 +1134,60 @@ static void clamp_id_aa64mmfr0_parange_to_ipa_size(ARMISARegisters *isar)
     SET_IDREG(isar, ID_AA64MMFR0, id_aa64mmfr0);
 }
 
+bool hvf_vhe;
+
+static void hvf_set_vhe(Object *obj, Visitor *v,
+                                   const char *name, void *opaque,
+                                   Error **errp)
+{
+    OnOffAuto mode;
+
+    if (!visit_type_OnOffAuto(v, name, &mode, errp)) {
+        return;
+    }
+
+    switch (mode) {
+    case ON_OFF_AUTO_ON:
+        if (__builtin_available(macOS 27.0, *)) {
+            hvf_vhe = true;
+        } else {
+            error_report("VHE emulation not supported on this system.");
+        }
+        break;
+
+    case ON_OFF_AUTO_OFF:
+        hvf_vhe = false;
+        break;
+
+    case ON_OFF_AUTO_AUTO:
+        /* Experimental feature as of macOS 27.0 */
+        hvf_vhe = false;
+        break;
+    default:
+        /*
+         * The value was checked in visit_type_OnOffAuto() above. If
+         * we get here, then something is wrong in QEMU.
+         */
+        abort();
+    }
+}
+
+static bool hvf_get_vhe(void)
+{
+    return hvf_vhe;
+}
+
+void hvf_arch_accel_class_init(ObjectClass *oc)
+{
+    hvf_vhe = false;
+
+    object_class_property_add(oc, "x-vhe", "OnOffAuto",
+        NULL, hvf_set_vhe,
+        NULL, NULL);
+    object_class_property_set_description(oc, "x-vhe",
+        "Configure experimental VHE enablement");
+}
+
 static bool hvf_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
 {
     ARMISARegisters host_isar = {};
@@ -1227,6 +1283,9 @@ static bool hvf_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
     if (hvf_nested_virt_enabled()) {
         /* SME is not implemented with nested virt on the Apple side */
         FIELD_DP64_IDREG(&host_isar, ID_AA64PFR1, SME, 0);
+        if (hvf_get_vhe()) {
+            FIELD_DP64_IDREG(&host_isar, ID_AA64MMFR1, VH, 0x1);
+        }
     }
 
     /*
@@ -1357,6 +1416,36 @@ hv_return_t hvf_arch_vm_create(MachineState *ms, uint32_t pa_range)
         }
     }
 
+    if (hvf_get_vhe()) {
+        Error *vhe_migration_blocker = NULL;
+        Error* errp;
+
+        void* hvf = dlopen("/System/Library/Frameworks/Hypervisor.framework/Versions/A/Hypervisor", RTLD_LOCAL);
+
+        if (!hvf) {
+            /* Unreachable. */
+            error_report("Failed to dlopen() Hypervisor.framework.");
+            goto cleanup;
+        }
+
+        /* Experimental API: might change before release. */
+        hv_return_t (*_hv_vm_config_set_vhe_enabled)(hv_vm_config_t cfg, bool vhe) = dlsym(hvf, "_hv_vm_config_set_vhe_enabled");
+        if (!_hv_vm_config_set_vhe_enabled) {
+            error_report("_hv_vm_config_set_vhe_enabled API not available.");
+            goto cleanup;
+        }
+        _hv_vm_config_set_vhe_enabled(config, true);
+
+        error_setg(&vhe_migration_blocker,
+        "Live migration disabled because VHE support is experimental");
+        if (migrate_add_blocker(&vhe_migration_blocker, &errp)) {
+            error_report("Failed to add migration blocker.");
+            goto cleanup;
+        }
+
+        dlclose(hvf);
+    }
+
     ret = hv_vm_create(config);
     if (hvf_irqchip_in_kernel()) {
         if (__builtin_available(macOS 15.0, *)) {
diff --git a/target/i386/hvf/hvf.c b/target/i386/hvf/hvf.c
index 150598418e..5a39a82492 100644
--- a/target/i386/hvf/hvf.c
+++ b/target/i386/hvf/hvf.c
@@ -1068,3 +1068,7 @@ void hvf_arch_remove_all_gdbstub_hw_breakpoints(void)
 void hvf_arch_update_guest_debug(CPUState *cpu)
 {
 }
+
+void hvf_arch_accel_class_init(ObjectClass *oc)
+{
+}
-- 
2.54.0 (Apple Git-156)

[PATCH v2 3/5] hvf: arm: advertise EL3 support when VHE is on

[Mohamed Mediouni]

This replicates the typical KVM configuration, and Hyper-V
wants it.

Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
---
 target/arm/hvf/hvf.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
index b61554e108..c54a92c2aa 100644
--- a/target/arm/hvf/hvf.c
+++ b/target/arm/hvf/hvf.c
@@ -1286,6 +1286,8 @@ static bool hvf_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
         if (hvf_get_vhe()) {
             FIELD_DP64_IDREG(&host_isar, ID_AA64MMFR1, VH, 0x1);
         }
+        /* Hyper-V doesn't launch if EL3 isn't advertised. */
+        FIELD_DP64_IDREG(&host_isar, ID_AA64PFR0, EL3, 0x1);
     }
 
     /*
-- 
2.54.0 (Apple Git-156)

[PATCH v2 4/5] hvf: arm: expose E2H0

[Mohamed Mediouni]

In the VHE mode, nVHE is not available. As such, only expose VHE.

Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
---
 target/arm/hvf/hvf.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
index c54a92c2aa..47eeaa0f30 100644
--- a/target/arm/hvf/hvf.c
+++ b/target/arm/hvf/hvf.c
@@ -1285,6 +1285,7 @@ static bool hvf_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
         FIELD_DP64_IDREG(&host_isar, ID_AA64PFR1, SME, 0);
         if (hvf_get_vhe()) {
             FIELD_DP64_IDREG(&host_isar, ID_AA64MMFR1, VH, 0x1);
+            FIELD_DP64_IDREG(&host_isar, ID_AA64MMFR4, E2H0, 0xf);
         }
         /* Hyper-V doesn't launch if EL3 isn't advertised. */
         FIELD_DP64_IDREG(&host_isar, ID_AA64PFR0, EL3, 0x1);
-- 
2.54.0 (Apple Git-156)

[PATCH v2 5/5] hvf: arm: ignore accesses to CNTKCTL_EL12

[Mohamed Mediouni]

This makes KVM work, with runnable virtual machines.

Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
---
 target/arm/hvf/hvf.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
index 47eeaa0f30..c32c705ddd 100644
--- a/target/arm/hvf/hvf.c
+++ b/target/arm/hvf/hvf.c
@@ -305,6 +305,10 @@ void hvf_arm_init_debug(void)
 #define SYSREG_CNTHCTL_EL2    SYSREG(3, 4, 14, 1, 0)
 #define SYSREG_MDCCINT_EL1    SYSREG(2, 0, 0, 2, 0)
 
+/* VHE registers */
+#define SYSREG_CNTKCTL_EL12 SYSREG(3, 5, 14, 1, 0)
+
+
 #define WFX_IS_WFE (1 << 0)
 
 #define TMR_CTL_ENABLE  (1 << 0)
@@ -1857,6 +1861,9 @@ static int hvf_sysreg_read(CPUState *cpu, uint32_t reg, uint64_t *val)
             assert_hvf_ok(hv_vcpu_get_sys_reg(cpu->accel->fd, HV_SYS_REG_CNTHCTL_EL2, val));
         }
         return 0;
+    case SYSREG_CNTKCTL_EL12:
+        /* Ignore for now */
+        return 0;
     case SYSREG_MDCCINT_EL1:
         assert_hvf_ok(hv_vcpu_get_sys_reg(cpu->accel->fd, HV_SYS_REG_MDCCINT_EL1, val));
         return 0;
@@ -2155,6 +2162,9 @@ static int hvf_sysreg_write(CPUState *cpu, uint32_t reg, uint64_t val)
             assert_hvf_ok(hv_vcpu_set_sys_reg(cpu->accel->fd, HV_SYS_REG_CNTHCTL_EL2, val));
         }
         return 0;
+    case SYSREG_CNTKCTL_EL12:
+        /* Ignore for now */
+        return 0;
     case SYSREG_MDCCINT_EL1:
         assert_hvf_ok(hv_vcpu_set_sys_reg(cpu->accel->fd, HV_SYS_REG_MDCCINT_EL1, val));
         return 0;
-- 
2.54.0 (Apple Git-156)

Re: [PATCH v2 0/5] hvf: arm: add experimental VHE (x-vhe) toggle

[Peter Maydell]

On Fri, 4 Sept 2026 at 05:37, Mohamed Mediouni <mohamed@unpredictable.fr> wrote:
>
> macOS 27.0 has a pre-release VHE implementation. Add support for it in QEMU.
>
> The first patch in the series is an independent bugfix that should be backported to QEMU 11.1 too.
>
> v2:
>
> Add:
> hvf: arm: expose E2H0
> hvf: arm: ignore accesses to CNTKCTL_EL12
>
> This is to have working KVM under the VHE configuration.
>
> Mohamed Mediouni (5):
>   hvf: arm: advertise ID_AA64PFR0_EL1.GIC
>   hvf: arm: add experimental VHE toggle
>   hvf: arm: advertise EL3 support when VHE is on
>   hvf: arm: expose E2H0
>   hvf: arm: ignore accesses to CNTKCTL_EL12

I would prefer to wait with this until the interface for
VHE is not a "private API you have to get at by playing
games with dlopen()" setup.

thanks
-- PMM